OLED device with improved light output

Abstract

An organic light-emitting diode (OLED) device is described, comprising: a) a substrate; b) an OLED formed over the substrate comprising a first electrode, a partially transparent second electrode through which light from the OLED is emitted, and at least one layer of organic light-emitting material disposed between the first electrode and partially transparent second electrode; and c) an encapsulating layer deposited on the partially transparent second electrode, wherein the encapsulating layer comprises one or more component layers, and wherein the encapsulating layer and the partially transparent second electrode combined have a transparency greater than the transparency of the partially transparent second electrode in the absence of the encapsulating layer, or wherein the encapsulating layer and the partially transparent second electrode combined have an absorbance less than the absorbance of the partially transparent second electrode in the absence of the encapsulating layer. To provide adequate encapsulation, in accordance with various embodiments of the invention at least one component layer of the encapsulating layer is deposited by atomic layer deposition, or the total thickness of encapsulating layer is at least about 150 nm. In a preferred embodiment, both such features are incorporated.

Description

FIELD OF THE INVENTION [0001] The present invention relates to organic light-emitting diode (OLED) devices and, more particularly, to a method of making an OLED device having improved light output and power distribution through a light-transmissive electrode. BACKGROUND OF THE INVENTION [0002] Organic light-emitting diode (OLED) devices, also referred to as organic electroluminescent (EL) devices, have numerous well-known advantages over other flat-panel display devices currently in the marketplace. Among the potential advantages are brightness of light emission, relatively wide viewing angle, reduced device thickness, and reduced electrical power consumption compared to, for example, liquid crystal displays (LCDs) using backlighting. [0003] Applications of OLED devices include active-matrix image displays, passive-matrix image displays, and area-lighting devices such as, for example, selective desktop lighting. Irrespective of the particular OLED device configuration tailored to th...

AI Technical Summary

Benefits of technology

[0025] Various embodiments of the present invention have the advantages that by employing an encapsulating layer specifically designed to increase transparency and/or decrease light absorbance in an adjacent electrode, light output from an OLED device may be increased. Various embodiments further enabl

Problems solved by technology

However, the current carrying capacity of such electrodes is limited, thereby limiting the amount of light that can be emitted from the organic layers.

Moreover, metallic layers may create unwanted cavity effects.

In contrast, typically polymeric materials have a moisture permeation rate of approximately 0.1 gm / m2 / day and cannot adequately protect the OLED materials without additional moisture blocking layers.

However, as taught in the prior art, such coatings might not be sufficiently conductive or transparent to provide or enable a transparent, conductive electrode.

However, this increases the area of the substrate and cover and is not completely effective.

This approach is less practical for top-emitters, since the desiccants, in that case, need to be highly transparent and uniformly distributed.

While highly light-transmissive electrode materials such as ITO have been proposed for top-emitting devices, ITO does not provide as high a conductivity as may be desired.

However, such microcavity designs require very precise control of layer thicknesses in order to obtain the desired color, and may also create a strong angular dependence on the color of light emitted, especially if broadband emitters are employed.

Further, it is still difficult to achieve a desired combination of high transparency and high conductivity, as such semitransparent structures typically do not transmit all of the light created in the OLED.

However, these absorption-reduction layers and dielectric layers cannot be used with an additional encapsulating layer because the optical characteristics of the structure are changed when the additional encapsulating layers are included and the absorption reduction effect is diminished or destroyed.

Moreover, prior art proposed ARL layers would typically not provide adequate desired encapsulation in view of the thickness and means of deposition typically employed.

However, these approaches all have the disadvantage of requiring that additional patterning steps be employed to form vias or to otherwise pattern the top electrode.

Moreover, they do not increase the optical efficiency of the OLED device as a microcavity does.

The use of light scattering techniques may increase the light-output efficiency of an OLED device but does not address the difficulty of providing a sufficiently transparent top electrode with adequate conductivity.

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